Display screen or portion thereof with a payment transaction graphical user interface



The FIGURE is a front view of a display screen or portion thereof with a payment transaction graphical user interface.

The broken line at the periphery of the FIGURE illustrates the display screen or portion thereof and the remaining dashed broken lines illustrate portions of the graphical user interface. None of the broken lines form part of the claimed design. 

CLAIM An ornamental design for a display screen or portion thereof with a payment transaction graphical user interface, substantially as shown and described. 